Polymerization of various silicic acids on biological templates

Abstract

Methods are disclosed for using biopolymers as templates for the polymerization of monomeric silicic acids. A method is provided wherein a biological polymer is used as a template. An inorganic polymer backbone forms a shell encasing the biopolymer template. The organic portion may be removed to leave inorganic nanotubes or other micro- or nano-scale structures which are the approximate size and shape of the template. The surface macrostructure of the biological template is duplicated in a silica shell—even molecular level imprinting is possible. The resulting silica structures have many uses, especially where micro- or nano-scale morphology should be controlled. Catalysts, semiconductors or metals may be deposited on the inside surface of the inorganic shell support. In another example, micro- or nano-particles that mimic the size and shape of the biopolymer template may be synthesized.

1 . A method for preparing an inorganic shell of an organic material template, comprising: 
 providing an organic material template;    contacting the organic material template with a silicon halide; and    hydrolyzing the silicon halide.    
     
     
         2 . The method of  claim 1  wherein the organic material template is a biopolymer; the inorganic shell optionally contains R 1  or R 2  groups; and the silicon halide is selected from the group consisting of compounds of the formula SiX 1 X 2 X 3 X 4 , SiX 1 X 2 X 3 R 1 , SiX 1 X 2 R 1 R 2 , and combinations thereof where X 1 , X 2 , X 3  and X 4  are independently selected from the group consisting of chlorine, bromine, and iodine; and R 1  and R 2  are independently selected from the group consisting of Lewis bases, alkyl or substituted alkyl groups, aryl or substituted aryl groups, and heterocyclic groups.  
     
     
         3 . The method of  claim 1  wherein a metal, catalyst or semiconductor is deposited on the organic material template.  
     
     
         4 . The method of  claim 1  wherein the organic material template is a biopolymer.  
     
     
         5 . The method of  claim 4  wherein the biopolymer is selected from the group consisting of cotton, silk, wool, cellulose, starch, DNA, RNA, proteins, cellular walls, micellular structures, wood, hair, fur, the exterior surface of microbes, sugars, polysaccharides, cyclodextrins, carbohydrates, polypeptides, polyols, polyamines, polyacids, polyamides, polyimides, and combinations thereof.  
     
     
         6 . The method of  claim 4  wherein the silicon halide is SiCl 4 .  
     
     
         7 . The method of  claim 5  wherein the inorganic shell is porous.  
     
     
         8 . The method of  claim 5  wherein the inorganic shell is mesoporous.  
     
     
         9 . The method of  claim 5  wherein the inorganic shell is microporous.  
     
     
         10 . The method of  claim 5  wherein the inorganic shell is nanoporous.  
     
     
         11 . The method of  claim 6  wherein the inorganic shell comprises a tube-shaped structure with an average interior pore diameter of less than about 15 μm.  
     
     
         12 . The method of  claim 1  wherein the organic material template is selected from the group consisting of cotton, silk, wool, cellulose, and combinations thereof.  
     
     
         13 . The method of  claim 1  wherein the organic material template is removed to leave a mold of the organic material template.  
     
     
         14 . The method of  claim 13  wherein the mold has a density approximately equal to the density of an aerogel.  
     
     
         15 . The method of  claim 13  wherein the mold has a density in the range of from about 0.002 g/mL to about 0.10 g/mL.  
     
     
         16 . The composition of matter comprising a shell of a biological material, further comprising: 
 silicon compounds in which the microscale or nanoscale form, morphology, texture, or topography of the biological material has been substantially replicated.    
     
     
         17 . The composition of matter according to  claim 16  wherein the biological material comprises a biopolymer; the molecular-scale, nanoscale, microscale or mesoscale form, morphology, texture, or topography of the substrate has been reproduced in a mold of the biopolymer comprising silicon compounds; and the biopolymer has been removed to leave only the mold.  
     
     
         18 . The composition of matter according to  claim 17  wherein the mold is a support for catalytic materials.  
     
     
         19 . The composition of matter forming a mold of a biological template substrate, comprising: 
 silica, silicates, silicic acids, or polysilicic acid, and mixtures thereof;    in which the microscale or nanoscale form, morphology, texture, or topography of the biological template substrate has been replicated.    
     
     
         20 . The composition of matter according to  claim 19  wherein the biological template substrate has been removed to leave only a mold of the biological template substrate and wherein the mold is comprised of silica.  
     
     
         21 . The composition of matter according to  claim 19  wherein the biological template substrate is a biopolymer.  
     
     
         22 . The composition of matter of  claim 20  wherein the mold of the biological template substrate has a density approximately equal to the density of an aerogel.  
     
     
         23 . The composition of matter of  claim 21  wherein the mold of the biopolymer has a density in the range of from about 0.002 g/mL to about 0.10 g/mL.  
     
     
         24 . The composition of matter of  claim 21  made by the method of  claim 6 .  
     
     
         25 . The composition of matter of  claim 19  characterized by mechanical stability and replication of molecular-scale surface detail of the biological template substrate.